Such methods are known for establishing a telephone connection to a mobile communications terminal device logged into a mobile communications network, in particular within a cellular mobile communications network. In these methods, the mobile communications terminal device is registered in the home location register of the mobile communications network. Moreover, its current position is precisely known down to a few cells of the cellular mobile communications network such that, after querying the home location register by means of a so-called paging (broadcast via multiple cells of the mobile communications network), a call connection may be initiated to the mobile communications terminal device via the mobile communications network.
Moreover, it is known to add supplements to telephone numbers. For example DE 197 11 096 A1 describes a method according to which it is checked whether the land, local or network area code is used in a telephone number when this number is called, the telephone number being dialed from the internal telephone book of the mobile communication terminal device. If the area code is missing it is automatically added to the telephone number. Otherwise, a communication setup originating from a visited mobile network, in particular a foreign network, is not possible or may lead to an undesired subscriber of the visited network. In this case, the area code forms a supplement, i.e. the supplement is part of the telephone number to be dialed. Furthermore, it is known from WO 01/37523 A1 and WO 2008/010217 A1 to add a supplement to a telephone number to activate or control a special service. WO 01/37523 A1 discloses a call-back service for roaming mobile subscribers, the service can be activated from a visited network into which the subscriber is logged. At first it is determined if the calling subscriber is logged into a home or visited network. In the latter case the telephone number to be dialed is extended by a service number/service address. WO 2008/010217 A1 discloses a similar call-back service for roaming mobile communication subscriber, wherein a service number is formed by a dummy-prefix and a service request code if the calling subscriber is logged into a visited mobile communication network. The service request code can be a valid telephone number.
In the known methods for establishing a telephone connection to a mobile communications terminal device, it is problematic that different networks can be responsible for monitoring and for conducting the method. Thus, when a call is attempted, for example, from a fixed-line network, the mobile telephone number is dialed and then a query of the home location register occurs within the mobile communications network in order to determine the cell location, i.e. the network area, into which the mobile communications terminal device to which the mobile telephone number has been assigned is logged. If the user of the mobile communications terminal device has established a call forwarding or the like, for example, to a mobile box on which a call may be recorded in the case of non-reachability, control of said alternative call routing occurs within the mobile communications network of the called party, with the caller having no influence on this process.
Conversely, it is problematic that, if control of the call is carried out by the fixed-line network and a call into mobile communications network is set up, it is not known whether, for example, the mobile communications terminal device is available and/or where it is located. Therefore, for example, a parallel call is usable only to a limited extent because, for example, routing the call back to the calling substation of the fixed-line network from which the call itself is originating would lead to termination of the call. This effect is also known as tromboning.